PROJECT SUMMARY Significance: Sleep disturbances are related to increased alcohol use (AU) and alcohol problems. The mechanisms that account for this association are not well understood. The proposed study will be the first to examine an integrative model including both a positive reinforcement pathway (i.e., higher impulsivity and increased sensitivity to the stimulating effects of alcohol) and a negative reinforcement pathway (i.e., higher anxiety and increased sensitivity to the anxiolytic effects of alcohol) that may link sleep disturbances and alcohol problems. We will use a rigorous multi-method approach that extends the laboratory into the real world. Results may directly inform AU treatment by identifying which specific sleep factors contribute to risk and why. Aims: For the positive reinforcement pathway, we hypothesize that later sleep timing and shorter sleep duration will predict higher impulsivity and greater increases in impulsivity and stimulation while intoxicated. For the negative reinforcement pathway, we hypothesize that lower sleep efficiency, a marker of insomnia, will predict higher anxiety while sober and increased anxiolytic response to alcohol. These processes will account for the association between sleep factors and concurrent and prospective AU outcomes. Specificity of the positive and negative reinforcement pathways will be examined. We will also explore if sex or diagnostic status (alcohol use disorder (AUD), sleep disorders) moderate the relationships between sleep characteristics and reinforcement pathways to AU. Approach: Young adult drinkers (21-30 years of age; 50% female; N = 150) will complete a protocol that includes ecological momentary assessments (EMA), laboratory sleep and alcohol response assessments, and 6-month follow-up. Participants will be current heavy episodic drinkers (i.e., 5+ days in past 30 days of consuming 5+/4+ for males/females; SAMHSA) to ensure sufficient range in alcohol outcomes of interest. We will use two 10-day EMA/actigraphy protocols to track daily sleep characteristics (timing, duration, and efficiency), anxiety, AU (freq. of 5+/4+ drinks/occasion), impulsivity, and subjective alcohol response in the real world. Each EMA protocol will conclude with an overnight sleep laboratory assessment followed by a within-subjects laboratory alcohol administration (counterbalanced: placebo/alcohol sessions) to examine alcohol response. During the chronobiology lab visits, we will use salivary DLMO to assess physiological circadian timing. During the alcohol lab visits, we will measure positive and negative reinforcement pathways via subjective response (stimulation/anxiety) and impulsivity (self-report, tasks). A 90- day timeline follow-back interview delivered 6 months later will allow for the prospective examination of associations between sleep characteristics and later AU (freq. of 5+/4+ drinks/occasion) and problems. The proposed study will provide novel information about how sleep disturbances, a set of modifiable factors, affect alcohol response and impulsivity. These findings may directly translate to prevention/treatment efforts for AUD.